The venue is the red dot.
Within the area enclosed by the yellow line, you can reach the venue in less than 10 minutes by foot.
The green dots indicate the main hotels nearby.
The blue line is the night tram service (#6) which operates all night on the Grand Boulevard in every 15 minutes so practically any place close to this line will be convenient.

Budapest has quite good night transportation service.
If you prefer public transportation (instead of walking or taxi), here's a map of night bus (and tram) lines to check the night time accessability of your hotels before booking. I hope you'll find it useful. (You can see the location of the venue in the opening post)http://www.bkk.hu/apps/docs/terkep/ejsz_sematikus.pdf
Eva